High-efficiency, directional microwave ablation antenna

Abstract

An electrosurgical device ( 10 ) operable to deliver microwave energy to cause targeted tissue ablation is provided. The electrosurgical device ( 10 ) comprises an antenna ( 26 ), a reflector ( 30 ), and a dielectric material ( 34 ) disposed therebetween. The selection of the dielectric material ( 30 ) and the relative positioning of the antenna ( 26 ) and the reflector ( 30 ) provide impedance matching between the antenna ( 26 ) and a transmission line ( 12 ) so as to minimize heating along the length of the device ( 10 ) during use.

We claim: 
     
       1. An electrosurgical device for tissue ablation comprising:
 a transmission line for transmitting an electromagnetic signal from a signal generator, the transmission line comprising a coaxial cable having an inner conductor, an outer conductor, and a dielectric material disposed therebetween; 
 an antenna coupled to the transmission line and configured for emitting electromagnetic energy therefrom sufficiently strong to cause tissue ablation; 
 an outer tubular body and an inner tubular member, the transmission line, antenna, and inner tubular member being located within the outer tubular body; and 
 a reflector comprised of a conductive material laterally spaced from the antenna and secured to or formed from the inner tubular member, the reflector being configured to reflect a portion of the electromagnetic energy emitted from the antenna and thereby provide a directional pattern of delivery of the electromagnetic energy to a target tissue, 
 the reflector having a cross-sectional configuration that is different than a cross-sectional configuration of a portion of the inner tubular member at the location that the reflector is secured to or formed from the inner tubular member, wherein the inner tubular member comprises a curvilinear cross-sectional configuration and the reflector has a rectilinear cross-sectional configuration. 
 
     
     
       2. The electrosurgical device of  claim 1 , wherein the reflector has a non-hemicylindrical cross-sectional configuration. 
     
     
       3. The electrosurgical device of  claim 1 , wherein the reflector comprises a different material than the inner tubular member. 
     
     
       4. The electrosurgical device of  claim 1 , wherein the reflector does not have a uniform cross-sectional configuration along a length thereof. 
     
     
       5. The electrosurgical device of  claim 1 , wherein the transmission line and inner tubular member cooperate to define a first annular region, and wherein the inner tubular member and outer tubular body cooperate to define a second annular region. 
     
     
       6. The electrosurgical device of  claim 5 , wherein the first annular region is configured to conduct a fluid in a first direction, and wherein the second annular region is configured to conduct the fluid in a second direction that is different from the first direction. 
     
     
       7. A method for ablating a tumor within a body comprising:
 inserting an electrosurgical device for tissue ablation into the tumor to be ablated, the electrosurgical device comprising:
 a transmission line for transmitting an electromagnetic signal from a signal generator, the transmission line comprising a coaxial cable having an inner conductor, an outer conductor, and a dielectric material disposed therebetween; 
 an antenna coupled to the transmission line and configured for emitting electromagnetic energy therefrom sufficiently strong to cause tissue ablation; 
 an outer tubular body and an inner tubular member, the transmission line, antenna, and inner tubular member being located within the outer tubular body; and 
 a reflector comprised of a conductive material laterally spaced from the antenna and secured to or formed from the inner tubular member, the reflector being configured to reflect a portion of the electromagnetic energy emitted from the antenna and thereby provide a directional pattern of delivery of the electromagnetic energy to a target tissue, 
 the reflector having a cross-sectional configuration that is different than a cross-sectional configuration of a portion of the inner tubular member at the location that the reflector is secured to or formed from the inner tubular member, wherein the inner tubular member comprises a curvilinear cross-sectional configuration and the reflector has a rectilinear cross-sectional configuration; 
 
 activating the electrosurgical device thereby causing the antenna to emit microwave energy along a predetermined angular expanse that is sufficiently strong to cause ablation of at least a portion of the tumor while positions of the antenna and the reflector remain fixed within the outer tubular body; 
 using sensing or imaging equipment to provide real-time feedback regarding a tissue ablation boundary during at least a portion of the time that the electrosurgical device is activated; 
 determining, using the real-time feedback from the sensing or imaging equipment, when the tissue ablation boundary extends to a desired edge of the target tissue; and 
 terminating the ablation or rotating the electrosurgical device to ablate the target tissue in another direction. 
 
     
     
       8. The method of  claim 7 , wherein the sensing or imaging equipment comprises magnetic resonance imagining equipment or one or more temperature sensing probes. 
     
     
       9. The method of  claim 8 , wherein the electrosurgical device is fabricated from MRI-compatible materials that do not generate a visible imaging artifact when introduced into an MRI bore. 
     
     
       10. The method of  claim 7 , wherein the sensing or imaging equipment comprises one or more fiber optic temperature probes. 
     
     
       11. The method of  claim 7 , further comprising circulating a cooling fluid within the outer tubular body. 
     
     
       12. The method of  claim 11 , wherein the reflector comprises a forward surface facing the antenna and a rearward surface facing away from the antenna, wherein the cooling fluid is circulated within the outer tubular body such that the cooling fluid contacts both the forward and rearward reflector surfaces.